1. Field of the Invention
The present invention relates to a diesel oxidation catalyst and an exhaust system provided with the same. More particularly, the present invention relates to a diesel oxidation catalyst and an exhaust system provided with the same that releases sulphur absorbed at an oxidation catalyst in high temperature by using hydrocarbon (HC) absorbed in low temperature.
2. Description of Related Art
Generally, exhaust gas flowing out through an exhaust manifold from an engine is driven into a catalytic converter mounted at an exhaust pipe and is purified therein. After that, the noise of the exhaust gas is decreased while passing through a muffler and then the exhaust gas is emitted into the air through a tail pipe. The catalytic converter is a type of diesel particulate filter (DPF) and purifies pollutants contained in the exhaust gas. A catalytic carrier for trapping particulate material (PM) contained in the exhaust gas is in the catalytic converter, and the exhaust gas flowing out from the engine is purified through a chemical reaction therein.
One type of catalytic converters is a diesel oxidation catalyst (DOC). The DOC oxidizes HC and CO contained in the exhaust gas.
Meanwhile, since sulphur contained in a fuel deteriorates performance of the oxidation catalyst, a noble metal including platinum (Pt) that has high sulphur tolerance is mainly used for the DOC. However, since platinum is expensive, manufacturing cost of the DOC becomes expensive. Therefore, the oxidation catalyst including platinum and palladium (Pd) is mainly used. In this case, deterioration in activity of the oxidation catalyst caused by sulphur is a major concern.
Particularly, deterioration in activity of the oxidation catalyst caused by sulphur is extremely large when temperature of the exhaust gas is low.
FIG. 6 is a graph showing relations between a temperature of an exhaust gas and a time required for recovering activity of an oxidation catalyst after poisoning of sulphur. As shown in FIG. 6, 5 minute is required for recovering activity of the oxidation catalyst in a case that the temperature of the exhaust gas is 400° C., 1 minute is required for recovering activity of the oxidation catalyst in a case that the temperature of the exhaust gas is 450° C., and 10 second is required for recovering activity of the oxidation catalyst in a case that the temperature of the exhaust gas is 500° C. Therefore, in order to use the oxidation catalyst including the platinum and the palladium, the temperature of the exhaust gas must be maintained higher than 450° C., but it is very difficult.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.